The isolation of proteins from source materials, such as, legumes and oil seeds, has been the subject of considerable research and a number of procedures have been suggested. One such procedure is the isoelectric precipitation of the protein by extracting the protein with aqueous alkali and then acidifying the extract to the isoelectric point of the protein. A more recent development, described in U.S. Pat. Nos. 4,169,090 and 4,208,323, assigned to the assignee of this application, involves the formation of an isolate under much milder conditions, using an aqueous food grade salt solution of ionic strength in excess of 0.2 M to extract the protein under weakly acid conditions, and dilution of the protein solution to form the isolate.
Protein isolates are characterized by high protein contents, namely at least about 90% by weight (as determined by Kjeldahl nitrogen.times.6.25), and have utility in various food compositions.